In a wireless communication system, there is a case where radio waves from a base station installed on a rooftop of a building are blocked by obstacles such as other buildings. This kind of problem becomes serious especially in urban areas or narrow streets. The areas in which radio waves are blocked by obstacles are called blind spots.
One of the methods dealing with this kind of problem is to use an RF booster. However, not only it is required that the RF booster include devices such as a receiver, an amplifier, a transmitter, etc., but also it is required that the RF booster be fed with power to operate, which generally leads to complexity and high cost. As a result, it is difficult to easily install many apparatuses of this kind of RF boosters in various places.
Also, there is a technology in which received radio waves are re-radiated in an intended direction by using a dual antenna system in which a receiving antenna and a transmitting antenna are combined (regarding this technology, refer to non-patent documents 1 and 2). Although the dual antenna system does not require power from the power supply, the amplifier, etc., it still requires a three dimensional structure with a complicated wiring pattern.
Therefore, a simple dual antenna system that is capable of receiving radio waves from a certain direction and capable of transmitting them in an intended direction is awaited in this technology field.